Method of preparing 2, 5-dichlorodioxane



Patented Jan. 28, 1947 UNITED STATES PATENT OFFICE METHOD OF PREPARING 2,5-DICHLORODI- OXANE William M. Smedley, Annapolis, Md.

7 Claims. 1

This invention relates to the preparation of 2,5-dichlorodioxane and derivatives thereof.

This application is a division of application 'Serial No. 351,154, filed August 3, 1940.

The compound 2,5-dichlorodicxane has the following general formula:

O 1 1120 6 2 HO] One of the, objects of the invention is to provide for the first time a method of preparin this compound in commercial yields. Other objects will appear hereinafter.

It has been found in accordance with this invention that 2,5-dichlorodioxane is produced in medium, the lower limit of the chlorination temperature will depend upon the availability of solvents which are liquid at the temperature of chlorination. Generally speaking, the preferred temperature of chlorination in accordance with the preferred embodiment of the invention, is

within the range from about C. to about 0., although in some cases the chlorination temperature may be carried as low as -80 C.

The invention will be further illustrated but is not limited by the following examples, in which the' quantities are stated in parts by weight unless otherwise indicated:

EXAMPLE I (a) Dioxane (100 g.; 1.14 mol; 100 cc.) was dissolved in carbon tetrachloride (159.5 g.; 1.04 mol; 100 cc.) and placed in a 500 cc. three-necked round-bottom flask equipped with condenser and mercury-sealed stirrer. Glass wool (0.2 g.) was added to create additional surface.

An ice-salt bath was used to cool the flask and contents to a temperature varying between 0 and 18 C.

Chlorine gas (300 g.; 4.23 mols) was added continuously over a period of forty hours. The flask was then chilled in a dry ice-ether bath and filtered. The crystals collected (M. P. 117-118; 52.66 g.) proved by chlorine analysis and diacetate formation to be 2,5-dichlorodioxane (yield 29.4%). Recrystallization was from chloroform.

(b) In a similar chlorination using a sintered glass disk on the chlorine inlet tube and a temperature of 47 C. the yield of 2,5-dichlorodioxene was higher (511.42g; 33.2%). When repeated at 7 C. the yield dropped (6.51 g.; 0.042 mols) to 3.65%.

(c) When chloroform cc.; 148.9 g.; 1.3 mols) was used as a solvent in place of carbon tetrachloride in the original chlorination (a) the yield of 2,5-dichlorodioxane (58.11 g.; 0.37 mol) was slightly increased (32.4%).

The structure of the 2,5-dichlorodioxane was proved by hydrolysis and quantitative conversion of the resulting glycol aldehyde to the p-nitrophenylosazone of glycolaldehyde. The structure of the compound was further proved to be 2,5- dichlorodioxane by its conversion to 2,5-diacetoxydioxane. Monochlorodioxane and other chlorinated dioxanes were found in the reaction product in smaller amounts. In all chlorinations resulting in the formation of 2,5-dichlor0dioXane very little hydrogen chloride appeared to escape from the reaction vessel apparently due to the use of.the low temperature. It appears to be important, therefore, to carry out the reaction at a temperature sufliciently low to prevent the splitting out of hydrogen chloride in any substantial amount.

The role of the solvent is not necessarily a passive one. At the low temperatures used the solubility of the hydrogen halide in the solvent may become quite large, thus increasing the concentration of the hydrogen halide in the reaction and depressing the formation of dioxene and hence the formation of 2,3-dichlorodioxane.

The 2,5-dichlorodioxane obtained as in Example I, when recrystallized from chloroform or petroleum ether, melted at 117118 C. The white needle-like crystals thus obtained when thoroughly freed of solvent, showed very little evidence of decomposition below 0 C. 'I'hecoms pound reacted with bromine in carbon tetrachloride solution to give a new compound, as yet unidentified.

The chlorination of 2,5-dichlorodioxane in various solvents resulted in the formation of small amounts of symmetrical tetrachlorodioxane.

The following example will illustrate the preparation of a 2,5-di-substituted-dioxane from 2,5- dichlorodioxane EXAMPLE II PREPARATION or 2,5-DIPHENYLDIOXANE A. Preparation of phenylmognesium bromide (a) Magnesium turnings (4.86 g.; 0.2 mol) were placed in a 500 cc. round-bottom threenecked flask, equipped with mercury-sealed stir- (100 cc.) was added to further dilute the phenylmagnesium bromide. V

B. Synthesis of 2,5-diphenyldiorane (a) Recrystallized 2,5-dichlorodioxane (12 g.; 0.0765 mol) was added cautiously in form of powdered crystals, to the ethereal solution of phenylmagnesium bromide. After all action had ceased the reaction mixture was decomposed with acidified water at C. and the ethereal layer separated and dried over activated calcium sulfate. Evaporation of the ether under reduced pressure gave crystals melting 114-14'7.

After one recrystallization from alcohol the compound melted at 147-152. The compound was obtained in th pure state after three recrystallizations from ethyl alcohol (95%) and one from dry ether, M. P. 173.5. vYield (12.5 g.; .052 mol) 68.1%.

Analysis: Calculated for CmH1sO2-mol. wt. 240.13 C 80.0, H 6.68; found239.'l C 79.96, H 6.86.

C. Study of the structure (a) Attempt hydrolysis. When dissolved in benzene (50 cc.) and refluxed with 1% potassium hydroxide solution (50 cc.) 2,5-diphenyldioxane (1 g.) did not hydrolyze appreciably in twelve hours. (0.92 g.) was recovered from the benzene layer.

(b) Attempt preparation of picrate. Saturated alcoholic solutions of 2,5-diphenyldioxane and picric acid were mixed. There was no appreciable reaction. Partial evaporation of solvent after two days resulted in the precipitation of 2,5-diphenyldioxane.

(0) General tests: Neither a glacial acetic acid solution nor an acidified alcoholic solution of 2,5-diphenyldioxane gave color reactions.

It will be recognized that many other 2,5-disubstituted-dioxanes may be prepared from 2 5- dichlorodioxane by replacement of the chlorine groups with other well known radicals, or groups, as, for example, alkyl 'groups, for instance, methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, undecyl, lauryl, myristyl, cetyl, oleyl and other saturated and unsaturated aliphatic groups. Other 2,5-diaryldioxanes may be prepared, as, for instance, the tolyl, xylyl'and naphthyl derivatives. The chlorine atoms of the 2,5-dichlorodioxane may also be replaced by substituted amino groups to form -2,5-di(amino substituted) dioxanes. The chlorine atoms of the 2,5-dichlorodioxane may also be, replaced by acyl groups, as, for instance, acetyl, lauroyl, benzoyl,

cinnamoyl and other acyl groups. It is thus apparent that the preparation of 2,5-dichlorodioxane opens up an entirely new field by the preparation of its derivatives. Some of these derivatives form polymers or resinous products.

In the chlorination of dioxane to form 2,5-dlchlorodioxane directly it is desirable to employ a liquid reaction medium which is a solvent for chlorine and which at the same time is substantially inert to chlorine. Good results have been obtained by the use of chlorinated hydrocarbons, e. g carbon tetrachloride, chloroform and ethylene chloride, and other hydrocarbons which Most of the 2,5-diphenyldioxane' are substantially inert under the conditions of the reaction, e. g., petroleum ether. It will be understood, however, that other solvents may be employed. The solvent. used may be a solvent both for chlorine and the reaction product, or it may be a solvent for the one and not the other. The chlorination may also be carried out without a solvent but the yields obtained have not beenashigh.

The amounts of chlorine employed in carrying out the halogenation may vary but should preferably be at least chemically equivalent to the amount of chlorine present in the desired product.

In the examples previously given, the direct chlorination of dioxane was carried out at atmospheric pressures. It will be understood. however, that superatmospheric pres-sures may be employed and are advantageous in increasing the concentration of hydrogen chloride in the reaction mixture.

While the invention is preferably carried out by using free chlorine as the chlorinating agent, it will be understood that other chlorinating agents may be used, as, for example, mixtures of chlorine and hydrogen chloride, sulfur monochloride and sulfuryl chloride (SOzClz). The reaction may be carried out either as a batch or a continuous operation.

In practicing the invention, where the 2,5-dichlorodioxane is to be used as an intermediate for another reaction, it is not essential that it be isolated from the reaction mixture. For instance, in the preparation of the sym, tetrachloro derivative of dioxane, the chlorination may be continued at a higher temperature. The compound dioxadiene has also been prepared by adding, directly to the reaction mixture containing the 2,5-dichlorodioxane without an isolation step, a basic dehydrohalogenating agent such as, for example, a weakly basic amine capable of splitting ofi the hydrogen chloride without causing substantialpolymerization.

- claim as new and desire to secure by Letters Patent of the United States is: I

1. A method of preparing 2,5-dichlorodioxane which comprises chlorinating dioxane directly at temperatures below 10 C.

2. A method of preparing 2,5-dichlorodioxane which comprises chlorinating dioxane directly with free chlorine in a solvent at temperatures below 10 C.

3. A method of preparing 2,5-dichlorodioxane which comprises directly chlorinating dioxane in a solvent medium at a temperature within the range from about +10 C. to about C.

4. A method of preparing 2,5-dichlorodioxane which comprises directly chlorinating dioxane in a solvent medium at a temperature within the range from about 10 C. to about 30 C.

5. A method of preparing 2,5-dichlorodioxane which comprises directly chlorinating dioxane in a chlorinated hydrocarbon solvent at a temperature below about +10 C.

6. A method of preparing 2,5-dichlorodioxane 

